Non-LTE Radiative Transfer with Turbospectrum

Gerber, Jeffrey M.; Magg, Ekaterina; Plez, B.; Bergemann, M.; Heiter, U.; Olander, Terese; Hoppe, Richard T.

doi:10.48550/arxiv.2206.00967

Cited by 3 publications

(4 citation statements)

References 50 publications

(67 reference statements)

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“…1 of Amarsi et al 2020b). They can be used readily with the 1D spectral synthesis code SME (Piskunov & Valenti 2017;Lind et al 2022), and could also be adapted to be used with Synspec (Hubeny et al 2021;Osorio et al 2022) and more recently Turbospectrum (Gerber et al 2022).…”

Section: Discussionmentioning

confidence: 99%

3D non-LTE iron abundances in FG-type dwarfs

Amarsi

Liljegren

Nissen

2022

A&A

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Iron is one of the most important elements in-stellar astrophysics. However, spectroscopic measurements of its abundance are prone to systematic modelling errors. We present three dimensional non-local thermodynamic equilibrium (3D non-LTE) calculations across 32 STAGGER-grid models with effective temperatures from 5000 K to 6500 K, surface gravities of 4.0 dex and 4.5 dex, and metallicities from −3 dex to 0 dex, and we study the effects on 171 Fe i and 12 Fe ii optical lines. In warm metal-poor stars, the 3D non-LTE abundances are up to 0.5 dex larger than 1D LTE abundances inferred from Fe i lines of an intermediate excitation potential. In contrast, the 3D non-LTE abundances can be 0.2 dex smaller in cool metal-poor stars when using Fe i lines of a low excitation potential. The corresponding abundance differences between 3D non-LTE and 1D non-LTE are generally less severe but can still reach ±0.2 dex. For Fe ii lines, the 3D abundances range from up to 0.15 dex larger to 0.10 dex smaller than 1D abundances, with negligible departures from 3D LTE except for the warmest stars at the lowest metallicities. The results were used to correct 1D LTE abundances of the Sun and Procyon (HD 61421), and of the metal-poor stars HD 84937 and HD 140283, using an interpolation routine based on neural networks. The 3D non-LTE models achieve an improved ionisation balance in all four stars. In the two metal-poor stars, they removed excitation imbalances amounting to 250 K to 300 K errors in effective temperature. For Procyon, the 3D non-LTE models suggest [Fe/H] = 0.11 ± 0.03, which is significantly larger than literature values based on simpler models. We make the 3D non-LTE interpolation routine for FG-type dwarfs publicly available, in addition to 1D non-LTE departure coefficients for standard MARCS models of FGKM-type dwarfs and giants. These tools, together with an extended 3D LTE grid for Fe ii from 2019, can help improve the accuracy of stellar parameter and iron abundance determinations for late-type stars.

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Section: Discussionmentioning

confidence: 99%

3D non-LTE iron abundances in FG-type dwarfs

Amarsi

Liljegren

Nissen

2022

A&A

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“…Abundances not included in Magg et al (2022) were taken from Asplund et al (2009). H, O, Mg, Ca, and Fe were computed following the non-LTE (NLTE) method described in Gerber et al (2022). The spectral synthesis calculations were made with the NLTE version of the TurboSpectrum code (Plez 2012;Gerber et al 2022), with a resolution R = 2 × 10 5 covering the 0.4-1.0 µm wavelength range.…”

Section: Description Of Data Productsmentioning

confidence: 99%

“…H, O, Mg, Ca, and Fe were computed following the non-LTE (NLTE) method described in Gerber et al (2022). The spectral synthesis calculations were made with the NLTE version of the TurboSpectrum code (Plez 2012;Gerber et al 2022), with a resolution R = 2 × 10 5 covering the 0.4-1.0 µm wavelength range. We computed the intensity spectra for 12 µ-points (µ = cos θ, where θ is the angle between the normal to the surface and the line of sight), distributed according to a Gauss-Radau distribution (GR12).…”

Section: Description Of Data Productsmentioning

confidence: 99%

First Release of PLATO Consortium Stellar Limb-darkening Coefficients

Morello

Gerber

Plez³

et al. 2022

Res. Notes AAS

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We release the first grid of stellar limb-darkening coefficients (LDCs) and intensity profiles (IPs) computed by the consortium of the PLAnetary Transits and Oscillations of stars (PLATO), the next medium-class (M3) mission under development by the European Space Agency to be launched in 2026. We have performed spectral synthesis with TurboSpectrum on a grid of MARCS model atmospheres. Finally, we adopted ExoTETHyS to convolve the high-resolution spectra (R = 2 × 105) with the state-of-the-art response functions for all the PLATO cameras, and computed the LDCs that best approximate the convolved IPs. In addition to the PLATO products, we provide new LDCs and IPs for the Kepler mission, based on the same grid of stellar atmospheric models and calculation procedures. The data can be downloaded from the following link: https://doi.org/10.5281/zenodo.7339706.

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“…PySME is one of only a few stellar spectral analysis tools available; others include Turbospectrum (Plez et al 1993;Plez 2012b;Gerber et al 2022), MOOG (Sneden 1973;Sneden et al 2012), Korg (Wheeler et al 2022), SYNSPEC (Hubeny & Lanz 2011, 2017Hubeny et al 2021), SYNTHE (Kurucz 1993d;Sbordone et al 2004), and SPECTRUM (Gray & Corbally 1994).…”

Section: Introductionmentioning

confidence: 99%

PySME

Wehrhahn

Piskunov

Ryabchikova

2023

A&A

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Context. The characterization of exoplanets requires the reliable determination of the fundamental parameters of their host stars. Spectral fitting plays an important role in this process. For the majority of stellar parameters, matching synthetic spectra to the observations provides a robust and unique solution for the fundamental parameters, such as effective temperature, surface gravity, abundances, radial and rotational velocities, among others. Aims. Here we present a new software package for fitting high-resolution stellar spectra that is easy to use, available for common platforms, and free from commercial licenses. We call it PySME. It is based on the proven Spectroscopy Made Easy package, later referred to as IDL SME or "original" SME. Methods. The IDL (Interactive Data Language) part of the original SME code has been rewritten in Python, but we kept the efficient C++ and FORTRAN code responsible for molecular-ionization equilibrium, opacities, and spectral synthesis. In the process we updated some components of the optimization procedure to offer more flexibility and better analysis of the convergence. The result is a more modern package with the same functionality as the original SME. Results. We applied PySME to a few stars of different spectral types and compared the derived fundamental parameters with the results from IDL SME and other techniques. We show that PySME works at least as well as the original SME.

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Non-LTE Radiative Transfer with Turbospectrum

Cited by 3 publications

References 50 publications

3D non-LTE iron abundances in FG-type dwarfs

3D non-LTE iron abundances in FG-type dwarfs

First Release of PLATO Consortium Stellar Limb-darkening Coefficients

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